Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...
Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ... Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...
82value may not be very accurate but could lead to an approximate estimate of the tensilestrength.4.4 Tensile Coupon Test Results4.4.1 Resulting Fracture SurfacesAll of the fractures of the historic wrought iron tensile coupon testing weresomewhat brittle in nature. The fractured surfaces were very jagged and uneven. Thesefractured surfaces, as seen in Figure 4.4, clearly show the “grain-like” characteristic ofthe wrought iron. The long deposits of iron silicate, known as slag, separated the ironinto fibers that appear to have torn during testing.Before any of the specimens were about to fail during testing, there was no visiblenecking or any typical pre-failure behavior that is typically found in structural steel.Figure 4.5 shows a typical ductile steel failure for a sample of steel tested with the sameprocedures as the wrought iron. As the photograph demonstrates, the steel failureconsisted of a considerable amount of necking, followed by an inclined failure plane thatis typical of ductile failures.The failure of wrought iron was more brittle in nature than the aforementionedsteel. During tensile testing, a slow tearing or ripping of what could be called the grainsof the wrought iron would start to occur and then the specimen would fail almostinstantaneously. In some cases, a crack would occur at the edge of the specimen in themiddle of testing and would remain until the specimen failed in a different area afterundergoing a considerable amount of strain. Figure 4.6 shows a typical failure of awrought iron tensile test coupon immediately after it occurred.
834.4.2 Overall Results from Tensile TestingA total of thirty-five tensile coupon tests were completed for this study. Of thethirty five tensile testing coupons, four had been heat straightened, five had been welded,and one had been mechanically straightened. Initially, all the specimens were comparedwithout differentiating between specimens that had been treated. In each tension coupontest the modulus of elasticity, yield strength, ultimate tensile strength, percent elongation,and strain hardening coefficient and exponent were determined. Tables 4.2 and 4.3 showthe results from the tensile coupon tests for the eyebar and round specimens.The first result determined from testing was the modulus of elasticity. Thismodulus is the slope of the elastic region of the stress strain curve for wrought iron. Theslope was found using linear regression methods, as performed with common spreadsheetsoftware, with the data found from the initial test of the tension coupons, as discussed inChapter 3.Figure 4.7 is a plot of the resulting modulus of elasticity from each tensile testingcoupon. In this plot, the results from the rectangular (eyebar) tensile coupons werecompared to the results from the round tensile coupons. The values for the modulus ofelasticity for all the tensile tests had very little variation between the square and roundtensile coupons. The average modulus of elasticity found from testing was 27,870,000psi with a standard deviation of 590,000 psi, which is only 2% of the average value.The second result determined from testing was the yield strength, which is thestress at which permanent deformations start to occur in the specimen. The yield strengthwas determined by offsetting a line, with the same slope as the Modulus of Elasticity, at astrain of 0.002 and determining where this line intersects the stress-strain curve. Figure4.8 is a plot showing the resulting yield strengths determined from testing for both therectangular and round tensile coupons. As seen in the plot, the yield strength values allfall between 25,000 psi and 35,000 psi, with little variation. The average of all the yield
- Page 52 and 53: 32Histogram of Kirkaldy Wrought Iro
- Page 54 and 55: 34Percent Occurance in Range - %45.
- Page 56 and 57: 3660Combined Wrought Iron BarsTensi
- Page 58 and 59: 38The Bell Ford Bridge consisted of
- Page 60 and 61: 40Two. These samples were taken fro
- Page 62 and 63: 42specimens were of constant cross
- Page 64 and 65: 44Along with rectangular tensile co
- Page 66 and 67: 46After the initial test loading wa
- Page 68 and 69: 483.6 Fatigue TestingTo develop a b
- Page 70 and 71: 50The final specimen category consi
- Page 72 and 73: 52This analysis was completed using
- Page 74 and 75: 54After the initial test was comple
- Page 76 and 77: 56completed, but before the surface
- Page 78 and 79: 58readings, load cell readings and
- Page 80 and 81: 60Figure 3.3 Donated Eyebars 4 and
- Page 82 and 83: 62Figure 3.7 Heated Areas in Blue o
- Page 84 and 85: 64Figure 3.11 Detail Used in Groove
- Page 86 and 87: 66900080007000y = 27.153xR 2 = 0.99
- Page 88 and 89: 68Figure 3.19 Charpy Impact Testing
- Page 90 and 91: 70Figure 3.23 Eyebar Connection in
- Page 92 and 93: 72Figure 3.27 Eyebar A After Filler
- Page 94 and 95: 74Figure 3.31 Side View of Finished
- Page 96 and 97: 76Figure 3.35 Front View of Eyebar
- Page 98 and 99: 78strength from the existence of pe
- Page 100 and 101: 80The carbon content present in the
- Page 104 and 105: 84strengths was found to be 29,940
- Page 106 and 107: 86wrought iron bars were investigat
- Page 108 and 109: 88stresses are induced. These perma
- Page 110 and 111: 90toughness the material. The test
- Page 112 and 113: 92From the finite element analysis,
- Page 114 and 115: 94Table 4.1 Chemical Analysis of Ey
- Page 116 and 117: 96Table 4.3 Tensile Coupon Test Res
- Page 118 and 119: 98Table 4.5 Charpy Impact Test Resu
- Page 120 and 121: 100Table 4.7 Comparison of Strain G
- Page 122 and 123: 102Figure 4.1 Typical Micrograph of
- Page 124 and 125: 104Figure 4.5 Fracture Surface of D
- Page 126 and 127: 106Comparison of Tensile Strengthfo
- Page 128 and 129: 108Combined Wrought Iron Bar Histor
- Page 130 and 131: 110Figure 4.17 Macrograph of Weld u
- Page 132 and 133: 112Figure 4.21 Cleavage Fracture of
- Page 134 and 135: Figure 4.25 Elongation of Hole in E
- Page 136 and 137: 116signs on or near the bridge that
- Page 138 and 139: 118testing of historic wrought iron
- Page 140 and 141: 120so that they would act in symmet
- Page 142 and 143: 122The reasons for the differences
- Page 144 and 145: 124The second corrosion pattern mod
- Page 146 and 147: 126Keating (1984) stated that the s
- Page 148 and 149: 128charcoal fire until it is red ho
- Page 150 and 151: 130Figure 5.3 Picture of Bottom Cho
834.4.2 Overall Results from Tensile TestingA total <strong>of</strong> thirty-five tensile coupon tests were completed for this study. Of thethirty five tensile testing coupons, four had been heat straightened, five had been welded,<strong>and</strong> one had been mechanically straightened. Initially, all the specimens were comparedwithout differentiating between specimens that had been treated. In each tension coupontest the modulus <strong>of</strong> elasticity, yield strength, ultimate tensile strength, percent elongation,<strong>and</strong> strain hardening coefficient <strong>and</strong> exponent were determined. Tables 4.2 <strong>and</strong> 4.3 showthe results from the tensile coupon tests for the eyebar <strong>and</strong> round specimens.The first result determined from testing was the modulus <strong>of</strong> elasticity. Thismodulus is the slope <strong>of</strong> the elastic region <strong>of</strong> the stress strain curve for wrought iron. Theslope was found using linear regression methods, as performed with common spreadsheets<strong>of</strong>tware, with the data found from the initial test <strong>of</strong> the tension coupons, as discussed inChapter 3.Figure 4.7 is a plot <strong>of</strong> the resulting modulus <strong>of</strong> elasticity from each tensile testingcoupon. In this plot, the results from the rectangular (eyebar) tensile coupons werecompared to the results from the round tensile coupons. The values for the modulus <strong>of</strong>elasticity for all the tensile tests had very little variation between the square <strong>and</strong> roundtensile coupons. The average modulus <strong>of</strong> elasticity found from testing was 27,870,000psi with a st<strong>and</strong>ard deviation <strong>of</strong> 590,000 psi, which is only 2% <strong>of</strong> the average value.The second result determined from testing was the yield strength, which is thestress at which permanent deformations start to occur in the specimen. The yield strengthwas determined by <strong>of</strong>fsetting a line, with the same slope as the Modulus <strong>of</strong> Elasticity, at astrain <strong>of</strong> 0.002 <strong>and</strong> determining where this line intersects the stress-strain curve. Figure4.8 is a plot showing the resulting yield strengths determined from testing for both therectangular <strong>and</strong> round tensile coupons. As seen in the plot, the yield strength values allfall between 25,000 psi <strong>and</strong> 35,000 psi, with little variation. The average <strong>of</strong> all the yield